Dewaxing of oil



' Patented Oct. 23, l9 34 1,978,010

1,978,010 nnwAinNG or'on. J Paul Johnson Carlisle, Niagara Falls, N. Y., as s signer, by mesne assignments, to E. I. du Pont de Nemours and Company, a corporation of- Delaware No Drawing. Application September 15, 1931, Serial No. 563,002 v 1Q Claims. (Cl. 196 -19) This invention relates to the treatment of hy- P s wh r y V y l w. 1d t st Oils eaii be drocarbon materials containing wax and more P duc d efiie tly an e o o c y om 11- particularly to the dewaxing of mineral oils. oet s d i Other e s w l appear Parafiin wax which may be defined as a mixer- 4 n 5 ture of hydrocarbons of the paraflin series, solid These Objects are acco p he y mixing the v at ordinary temperatures, is often obtained by r l x oil with methylene ehloride s, dewaxing hydrocarbon oils. The procedure gen- (CHzCls), alone or in mixture with other wax orally used i to add to the oil-wax mixture a deen s, subj c g the xture to oderately waxing solvent or solvent mixture in which the l w mperatures and removin W m' imta I oil is very soluble, and the wax is but slightly from the -methylene chloride mixture. 65 soluble. The resulting mixture is then cooled to n o e m th d f arrym s ut my v ti somelow temperature and'the wax removed by. t ene chloride is'mixed with the oil, for filtration r centrifu i I example, in the proportion of'50-80% methylene "Isopropyl and butyl alcohol; acetone, is opropy1 ehlgride to 50-29% y Volume of Oil-s e l ether, or mixtures of these with benzol or naphture is n Chllled to a temp ra u of 32 F- 7 tha have been suggested as solvents toreplace lower and the W .p pl moved from naphtha Many ofthes solvents or mixtures the oil-solvent mixture for instance by filtration 'ofsolvents are capable of separating wax from at he chilling temperature. The wax is Pr pioil at relatively high temperatures. However, 'tat d in a su tan ally ys a l n r makms '20 under these conditions the solubility of the oil p e a p a ca y c pl te s pa at of wax &-

' isso low that a very large volume oi solvent per d o lven mix ure in a in l p n, f unit volume of oil is necessary in order to obmp y fil i n T m yl hl rid tain satistactory'separation of the oil' and wax. y then be moved om the Oil for instance Solvents such as benzene or naphtha are miscible by mpl di lla Steam distillation, 1

" with oil but require very low chilling temperablowing, followed by recovery of the methylene 80- tures such as "60 F. to -'10 F. to eireotively chloride y any su ta nsremove the wax and produce low pour point oils. mmpze's This procedure is also objectionable because the W D p teproduced is generally amorph us I 1. A lubricating distillate having a specific and difiicult toremovetfrom the oil and solvent gravity of 0.852 and a pour point of 70 F. was

by fi t at d Other epeletiolls involving mixed with methylene chloride in the proportion f sweating, which includes in standing, olof 1 volume of oil to 1 volume of methylene chloing and refiltering this wax-oil mixture which id h mixture w cooled t t t y have retained about 50% of il, and r peat-- rate of 18 F. per hr. and filtered after standing i c operations until e desired at n sat v-13" F. for one hour. The wax obtained by obteinedfiltration was white'and contained 11% of on. 7

C rtain eh ydrocarbon solvents among After removal of the methylene chloride by dis- I which are ethylene chloride and trichlorethylene t n t currentpf dry air, t pour point alone or in conjunction with other solvents, have of th filt r 11 w found t be 5 F, The

s been P p as Solvents- These ehlorehyoil ShOWQdPIlO discoloration by this treatment 95 dmcelbons as heretofore tried have not been nor was there any evidence of discoloration after considered s isf ry because oils treated with continued standing. A sample of lubricating disthe te o darken in t a 1 tillate treated in the same manner with four An b ect r thi i v n i n i to p vide avolumes of naphtha yielded an oil having a pour process for preparinglow cold test lubricating point of 513 j 100 I oils from cylinder stocks. lubricating distillates o volume of n of Example 1 w i 1 and the like 1' hi @016 test using ie solved in 2 volumes of methylene chloride and y higher Chilling p ra s than these e dewaxed as described in Example 1. The dewaxed erally employed in pr s n 'igl iee- A fur her .011 had a pour point of -5 F. The wax residue,

'50 object is to obtain a sufliciently distinct separaafter washing at -l3 F. with two volumes of tion'of wax i m he il to iv a high yield of methylene chloride to displace the solvent and low cold' test oil and commercially usable wax oil.in the cake, had a melting point of 108 1'', without resorting to the slow and complicated It was white and crystalline and contained 3% fractional melting or sweating operations now of oil.

in use. A still further object is to provide a 3. One volume of the oil oi Example 1 was no 4. One volume of a cylinder stock having agravity of 29.5 A. P. I., a pour point of 90 F., and a viscosity of 98 seconds S. U.-V. at 210 F. was dissolved in 2-volumes of methylene chloride and chilled at the rate of 18 F. per hour to -13 F. After standing at-13 F. for 1 hour, the wax precipitate was removed by filtration. Upon'removing the solvent by distillation in a stream'of nitrogen the oil was found to have a pour point of 0 F. The wax was crystalline and .brown in color.

5. One volume of long residuum was dissolved in two volumes of naphtha, having a flash point of 115 F. and a boiling point of 154-201 C. and cooled to l3 F. The filtrate became cloudy, indicating the presence of amorphous wax. This wax wasso finely divided that it could not be separated from the oil by filtration.

One volume of this long residuum was dissolved in two volumes of methylene chloride and chilled to -13' F. A brown crystalline wax was precipitated which was easily removed by filtration. The pour point of the dewaxed ,oil was 0 F.

While methylene chloride alone is'particularly effective for removing wax from oil, it may also be used in' admixture with other commonly employed organic wax solvents. For example, mixtures of methylene chloride with acetone, butanol, benzol or naphtha are suitable. Varied proportions of methylene chloride may be employed in the solvent mixture. Satisfactory results have also been obtained by using varied ratios of solvent to oil, for examplefl to 4 parts solvent to 1 part oil.

.If satisfactorily conducted, my separation of oil and wax will enable one to recover a good grade wax in one operation. -If however, a further removal of oil from wax is desirable, I have found that washing or recrystallizing this wax with methylene chloride alone or admixed as stated above, will effect any further desired separation. The following examples will further illustrate the invention: a.

6. One liter of long residuum with a pour poin of 90 F. was dissolved in a mixture of 1.6 liters of methylene chloride and 0.4 liter of acetone.- This mixture was allowed to cool at a rate of 18 F; an hour until the temperature of 13 F. was

reached. It was allowed tostand forone hour and then filtered. The wax removed was brown and crystalline at the dewaxing temperature.

The dewaxing solvent mixture was removed from the oil by distillation at 176 F. in a current of air. The resulting oil showed no signs of discoloration. It had a pour point of 15 F.

'7. One liter of the long residuum of Example 6 was treated with a mixture of one liter of oil had a pour point of l0 F.

8. One liter of wax distillate was dissolved in a mixture of 1.6 liters of methylene chloride and 2.4 liters of acetone. This mixture was allowed to cool at the rate of 18 F. an hour to 13 F. The wax,'which was immediately filtered off, was white and crystalline and had a melting point of 103 F. The dewaxing solvent was then removed by distillation at C. in a current of air. The resulting oil had a pour point of 25 F.

Thisinvention is not limited to any particular type of materials but is generally applicable to removal or recovery of petrolatum or wax from mineral oils such as wax distillates, long residuums; lubricating oils and the like by filtration, cold settling, centrifuging, or other means. It is likewise not limited to specific solvent-oil ratios, chilling temperatures, and chilling rates, since these are dependent upon the character of the wax-bearing oil.

My invention has many advantages over prior methods. One advantage is that by the use of my invention, low cold test oils can be obtained without resorting to the. low temperatures necessary with solvents such as naphtha. The relative amount of solvents such as acetone, butanol, or ethylene dichloride required for dewaxing, is very much greater than is necessary with methylene chloride.

Another important advantage is that a sharp separation of oil and wax can be obtained in one operation, thus insuring a high yieldof dewaxed oil and the, direct production of a salable, crystalline wax without resorting to the slow and cumbersome sweating operation now in use for recovering oil and high grade wax from the wax precipitate. 'Another important advantage resides in the fact that the wax precipitate obtained in myprocess is crystalline and can be filtered much more readily than the amorphous wax obtained for instance from naphtha solutions. Still further advantages of methylene chloride over other solvents for dewaxing lie in its non-inflammability, high specific gravity, inertness toward oil, and non-corrosiveness to metals. Mixtures co I taining methylene chloride and other solvents as indicated above possess similar advantages and are' cheaper than methylene chloride alone.

To avoid undue multiplicity of claims, I intend the term methylene chloride to cover this material either when used alone or when used in substantial and eiiective quantities in admixture in varying proportions with other suitable solvents as hereinbefore indicated.

I claim:

1. A process for separating the oil and wax in a wax-oil mixture comprising dissolving methylene chloride therein, cooling the wax-oil-methylene chloride mixture to cause the precipitation of the wax, and thereafter separating the precipitated wax.

k 2. A process for separating the oil and wax in 135 I aFwax-oil mixture comprising dissolving methylene chloride therein, chilling the wa'x-oiI-methylene chloride mixture to a temperature below 32 Fahrenheit to precipitate the wax, andthereafter removing the precipitated wax from the mixture.

3. A process for separating the oil and wax in a wax-oil mixture comprising dissolving methylene chloride therein, chilling the wax-oil-methylene chloride mixture to a temperature below 32 14.5

Fahrenheit to precipitate the wax, removing the "wax and washing said wax with methylene chloprising mixing 1 to 4 volumes of methylene chlo- 1.50

- mixture to a temperature below 32 1". and filtering precipitated wax from the mixture.

5. Process for treating wax-oil mixtures comprising mixing 1 to 4 volumes of methylene chloride with 1 volume of said mixture, chilling the mixture to a temperature below 0 F. and filtering precipitated wax from the mixture.

6. In a method for the purification of wax containing oil as the principal impurity, the step of adding methylene chloride to said wax and cooling to a temperature below 32 F. and removing the methylene chloride solution, in order to remove therefrom the impurities soluble in methylene chloride.

'1. In a process of wax removal from a mineral oil-wax mixture utilizing methylene chloride as a dewaxing agent, the step comprising washing the precipitated'wax with further amounts of methylene, chloride. Y

8. The process for separating the oil and wax in a wax-oil mixture comprising adding methylene chloride to thewax-oil mixture, cooling the wax-oil-methylene chloride mixture to a temperature below 32 Fahrenheit to precipitate the wax, removing the precipitated wax from the mixture and thereafter separating the methylene chloride from the oil.

9. The process for separating the oil and wax in a wax-oil mixture comprising dissolving methylenechloride therein, cooling the wax-oil-methylene chloride mixture to a temperature below 32 Fahrenheit to cause precipitation of the wax, re-

moving the precipitated wax and washing said wax with methylene chloride and thereafter separating the methylene chloride from the oil.

10..Process for treating wax-oil mixtures com PAUL JOHNSON CARHSLE; 

